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Biomedical subjects

B Hamm

Publications and source records attributed to B Hamm.

At least 199 records · Page 11Linked to original sources
PubMed1992

[Tumors of the adnexa--a comparison of magnetic resonance tomography, endosonography and the histological findings].

43 patients suspected clinically of having tumours of the adnexa were examined by MR and 40 by endosonography in a prospective study. All underwent surgery. Correct lateralisation of the tumour was achieved by MR in 39 out of 43 cases (91%) and by endosonography in 32 out of 40 cases (80%). By means of MR it was possible to recognise the affected organ in 79%, and by vaginal sonography in 70% of women. Prediction of malignancy was possible with MR in 39 out of 43 cases (91%) and by endosonography in 30 out of 40 cases (75%). Infiltration into the omentum and gut and peritoneal metastases was missed by both methods (4 out of 4 cases).

Adnexa Uteri↗
PubMed1992

[Primary and secondary tethered cord syndromes. Their nuclear magnetic tomographic diagnosis and comparison with the surgical findings in 40 patients].

The MRT findings in 40 patients with the tethered cord syndrome (TCS) have been compared with the operative findings. In cases of primary TCS (17 patients), MRT showed a low conus medullaris in 15 cases and this was confirmed surgically in 14. Other abnormal findings were lipomas (MRT 12/operatively 13), diastematomyelia (MRT 2/operatively 2) and thickened filum terminale (MRT 6/operatively 3). In secondary TCS (23 patients) postoperatively adhesions were prominent (MRT 16/operatively 23) while low position of the conus was found by MRT in 19 and surgically in 18 patients. Other findings were lipomas (MRT 5/operatively 6), epidermoids (MRT 2/operatively 2) and diastematomyelia (MRT 2/operatively 0). Agreement between MRT and operative findings regarding fixation of the spinal cord is closer in primary TCS (15/17, 88%) than in secondary TCS (16/23, 69%).

Adolescent↗
PubMed1992

Focal liver lesions: MR imaging with Mn-DPDP--initial clinical results in 40 patients.

Manganese (II) N,N'-dipyridoxylethylenediamine-N,N'-diacetate-5,5'-bis(phosphate) (DPDP) was evaluated as a contrast agent for magnetic resonance (MR) imaging (1.5 T) of focal liver lesions in 40 patients. Doses of 5 and 10 mumol/kg were administered intravenously. Mn-DPDP-enhanced T1-weighted images were compared quantitatively and subjectively with standard T1- and T2-weighted nonenhanced images. Use of Mn-DPDP resulted in a statistically significant increase in signal intensity of liver parenchyma in T1-weighted images at both doses. No enhancement was seen in metastases, cholangiocarcinomas, or lymphomas, while all hepatocellular carcinomas were enhanced. Enhancement was seen in focal nodular hyperplasia and in regenerative nodules. The lesion-to-liver contrast in Mn-DPDP-enhanced gradient-recalled-echo images was superior to that of all precontrast images (P less than .01). The number of nonenhancing malignant liver lesions detected in spin-echo (SE) images was increased (272 in T2-weighted SE images vs 390 in T1-weighted Mn-DPDP-enhanced SE images). Image interpretation (eg, visualization and demarcation of the lesions) was markedly better in Mn-DPDP-enhanced images than in all precontrast images (P less than .001).

Adult↗
PubMed1992

Multisection FLASH: method for breath-hold MR imaging of the entire liver.

One hundred ten patients with various focal liver lesions were imaged with a multisection fast low-angle shot (FLASH) gradient-echo sequence with an echo time of 4.6 msec. This sequence enabled the acquisition of 19 T1-weighted magnetic resonance (MR) images of the liver within a single 26-second breath hold. Patients were also examined with standard T1- and T2-weighted spin-echo (SE) sequences. The multisection FLASH sequence provided significantly higher (P less than .01) liver-spleen contrast, liver-spleen signal-difference-to-noise ratio (SD/N), liver-tumor contrast, and liver-tumor SD/N than the T1-weighted SE sequence but lower values than the T2-weighted SE sequence. Motion artifacts were reduced with the multisection FLASH sequence compared with both SE sequences (P less than .01). The overall image quality of the multisection FLASH images was similar to that of the T1-weighted SE images and superior to that of T2-weighted SE images. The most important characteristics of the multisection FLASH technique in MR imaging of the liver are the high T1 contrast, the prevention of motion artifacts, and a dramatic reduction in imaging time.

Adult↗
PubMed1992

MR lymphography with iron oxide particles: dose-response studies and pulse sequence optimization in rabbits.

Superparamagnetic iron oxide (SPIO) particles are a promising contrast agent for MR lymphography. The effect of SPIO on MR imaging of normal lymph nodes and the impact of the size of the dose have not yet been investigated in detail. Therefore, we performed dose-response and pulse sequence optimization studies. MR images of the iliac lymph nodes of 15 normal rabbits were obtained at 1.5 T with 12 different spin-echo (SE) and gradient-echo (GRE) sequences before and after SPIO administration. The contrast agent was injected into a femoral lymph vessel at five different doses (0.02-2.0 mumol Fe/animal). The dose that reduced signal intensity by half (ED50) was determined for each sequence, and images were evaluated qualitatively. Doses of 0.2 and 1.0 mumol Fe caused a complete signal loss throughout the lymph node. In this dose range, proton density-weighted SE sequences showed a profound signal loss (ED50, 0.132 mumol Fe), and lymph nodes were sharply demarcated. The GRE sequences (ED50, 0.027-0.070 mumol Fe) and the T2-weighted SE sequence (ED50, 0.014 mumol Fe) showed an even more pronounced signal loss but insufficient anatomic resolution. Underdosing (less than or equal to 0.1 mumol Fe) caused only a focal signal loss in the lymph nodes. Oversaturation (2.0 mumol Fe for SE sequences, greater than or equal to 1.0 mumol Fe for GRE sequences) led to image distortion and did not allow assessment of lymph node morphology. Our results show that optimal contrast enhancement of normal lymph nodes with SPIO can be achieved in the dose range of 0.2-1.0 mumol Fe on proton density-weighted SE sequences. Our results may serve as a basis for further development of noninvasive MR lymphography.

Animals↗
PubMed1992

Dynamic MR imaging of the abdomen with gadopentetate dimeglumine: normal enhancement patterns of the liver, spleen, stomach, and pancreas.

To show the normal contrast enhancement patterns of the upper abdominal organs, dynamic gadopentetate dimeglumine-enhanced MR imaging of the upper abdomen was performed in 48 patients. Although all patients were originally examined for focal hepatic lesions, none of them had diffuse parenchymal disease of any of the examined organs. Dynamic gadopentetate dimeglumine-enhanced MR imaging was done by using a heavily T1-weighted gradient-echo sequence (100/5 [TR/TE], 80 degrees flip angle) performed before, and repeatedly for a period of 10 min after, an IV bolus injection of gadopentetate dimeglumine (0.1 mmol/kg). Signal enhancement in each of the organs was calculated by measuring the signal intensity before and after administration of contrast medium. All organs showed signal enhancement within the first 2 min (p less than .001) and a continuous decline thereafter. The enhancement of the pancreas, liver, stomach wall, spleen, and renal cortex reached peaks of 75%, 78%, 96%, 144%, and 216%, respectively, 45 sec after administration of contrast medium. Liver and pancreas showed a homogeneous enhancement pattern throughout the examination. The spleen appeared heterogeneous during the first 60 sec and homogeneous thereafter. Two zones could be distinguished on the contrast-enhanced images of the stomach wall: an enhanced inner zone and an unenhanced outer zone. We conclude that homogeneous enhancement of the liver and pancreas, early heterogeneous enhancement of the spleen, and enhancement of the inner gastric wall are normal patterns on dynamic gadopentetate dimeglumine-enhanced MR images.

Contrast Media↗
PubMed1992

Contrast materials for cross-sectional imaging of the abdomen.

The development and clinical studies of contrast agents for cross-sectional abdominal imaging presently focus on the diagnosis of liver diseases and suitable oral contrast agents for MR imaging. The well-known paramagnetic agent, gadopentetate dimeglumine is now used for improving the differential diagnosis of liver lesions such as focal nodular hyperplasia in dynamic MR studies. Preclinical studies and initial clinical trials indicate that the new paramagnetic hepatobiliary contrast agent, manganese dipyridoxal diphosphate, might improve the sensitivity of MR imaging in the detection of liver lesions. With respect to dynamic contrast-enhanced CT in the detection of liver lesions, interest has focused on the question of the optimal scanning technique. Promising results have been obtained in initial studies of contrast agents for sonography, called microbubbles. This substance produces good visualization of the vascular status of liver tumors. Nuclear medicine somatostatin receptor imaging may be of special clinical interest because it allows even very small somatostatin-positive metastases to be detected and thus provides specific information for therapy planning in patients with positive scan results. Initial studies have shown that using contrast enhancement with MR imaging of the pancreas improves the contrast between pancreatic tissue and lesions. Manganese dipyridoxal diphosphate is taken up by pancreatic tissue, though the exact mechanism remains to be clarified, and may therefore have potential as a future MR contrast agent for evaluation of the pancreas. A number of oral MR contrast agents have now been tested in larger clinical trials. Both positive and negative oral agents are safe and well tolerated and achieve the aim of reliably delineating the gastrointestinal tract from other organs and pathologies in the abdomen.

Abdomen↗
PubMed1992

[The value of magnetic resonance tomography in the detection and differential diagnosis of focal liver lesions].

Magnetic resonance imaging (MRI) of the liver has made considerable progress due to improvements in the examination technique. Sensitivity for the detection of focal liver lesions is higher for MRI than for CT. In the differential diagnosis of liver tumors MRI is remarkably accurate. This is particularly true for hemangiomas, liver cell carcinomas and focal nodular hyperplasias. From a clinical view point differentiation between hemangiomas and metastases is of utmost importance. Future improvements in MR diagnosis of liver diseases are expected due to fast imaging techniques and liver-specific contrast agents.

Diagnosis, Differential↗
PubMed1991

[Diagnosis of focal liver lesions. The value of imaging systems].

Selection of the suitable modality for the detection or differential diagnosis of focal liver lesions must consider, in addition to its accuracy, such factors as on-site availability, the costs involved, and the stress to the patient. The preferred screening technique is ultrasonography which, however, has a high failure rate, in particular in the case of small lesions. In many cases computed tomography (CT) permits the correct diagnosis to be established. Both CT and ultrasonography make possible selective percutaneous biopsy. Magnetic resonance imaging is one of the most sensitive procedures, but is often not available - even in specialized centers. With this technique or blood pool scanning, hepatic hemangiomas found incidentally can be diagnosed in 90% of the cases. The diagnosis of focal modular hyperplasia continues to be difficult.

Diagnosis, Differential↗
PubMed1991

[Variability and reproducibility in the determination of left-ventricular heart volume by cine-MR. A comparison of measurement methods].

Sixteen normal individuals were examined on a 1.5 T instrument using gradient echo sequences (cine-MR). The results of various computations were tested with respect to agreement and reproducibility of the methods. The ejection fractions calculated from bi-plane and 3-dimensional reconstructed volumes showed very low standard deviations of mean values (SD less than 2%). Volumes calculated from a single plane produced the greatest scatter of mean values (SC approximately 5%). In all sixteen subjects, the MR findings showed good reproducibility. There was very little inter-observer variability (variability less than 5%). A comparison of various methods showed that bi-plane and monoplane volume calculations obtained by MR in the cardiac axis are more accurate than those obtained by echocardiography (MR:R greater than 0.75, p less than 0.001; echo:R less than 0.75, p greater than 0.05).

Adult↗
PubMed1991

[The diagnosis of bladder carcinomas by NMR tomography: an improvement with Gd-DTPA?].

85 patients suffering from urinary bladder carcinoma were examined by magnetic resonance imaging in a prospective study. Following precontrast diagnosis, 15 patients were given an intravesicular application of gadolinium-DTPA (Gd-DTPA). Another 35 patients received an intravenous bolus of GD-DTPA. A diagnostic advantage was achieved in only 2 of 15 tumours by using intravesicular contrast application. Compared to the precontrast diagnosis, a 14% improvement from 69% (precontrast) to 83% (contrast medium) was seen with Gd-DTPA applied intravenously in the diagnosis of the tumour stage. The diagnostic gain lies in the improved tumour recognition, the improved demarcation of papillary, non-muscle-infiltrating tumours and in the more definite diagnosis of infiltration into neighbouring organs and the pelvic wall. Demarcation of perivesicular fatty infiltration is rendered more difficult by Gd-DTPA.

Administration, Intravesical↗
PubMed1991

[MR tomography of the liver at 1.5 tesla. The value of T1-weighted imaging with a fast multislice gradient-echo sequence during respiratory standstill].

The diagnostic value of a fast multislice gradient-echo sequence was compared with that of conventional spin-echo sequences in a prospective study of 76 patients. With the multislice gradient-echo sequence, the entire liver can be examined in less than 3 minutes since five sections can be imaged during one breath-holding period. The strongly T1-weighted gradient-echo sequence (GRE 100/5/80 degrees) yields a significantly better T1-contrast than the T1-weighted spin-echo sequence (SE 500/15) (p less than 0.01) and thus improves the visualization of liver lesions. Another major advantage of the fast gradient-echo sequence is the pronounced reduction of motion artefacts.

Chi-Square Distribution↗
PubMed1991

[The clinical value of Mn-DPDP: a new paramagnetic hepatobiliary contrast medium for magnetic resonance tomography of the liver].

In an open prospective study the tolerance and diagnostic value of the new hepatobiliary contrast agent Mn-DPDP in MR imaging was evaluated in 20 patients suspected of having focal liver lesions. T1- and T2-weighted spin-echo sequences and T1-weighted gradient-echo sequences were obtained before and after intravenous application of Mn-DPDP. In all patients the signal to noise (S/N) values of normal liver tissue increased significantly after application of Mn-DPDP. All focal lesions could be better localized and differentiated due to increased contrast to noise ratios of lesion to liver. Pathological examination revealed in 14 patients malignant and in 5 patients benign liver lesions; one patient had no pathological findings. In metastatic disease of the liver 25-120% more lesions could be detected in MRI after Mn-DPDP-application, compared with the unenhanced images. In 5 patients the lesions showed significant enhancement of Mn-DPDP (2 cirrhotic nodules, 2 hepatocellular carcinomas, 1 focal nodular hyperplasia). Our preliminary results indicate that Mn-DPDP is a well-tolerated contrast agent useful for the detection and differentiation of liver lesions in MR imaging.

Adult↗
PubMed1991

Carcinoma of the uterus: use of gadopentetate dimeglumine in MR imaging.

This prospective study assessed the role of gadopentetate dimeglumine-enhanced magnetic resonance imaging in the detection and staging of carcinomas of the endometrium and cervix. Surgical-pathologic findings were used as the standard of reference. In the evaluation of endometrial carcinoma, contrast-enhanced imaging improved tumor detection and differentiation between viable tumor and retained debris. Use of contrast material significantly improved the staging accuracy. The ability to assess the depth of myometrial invasion was also improved. In the evaluation of cervical carcinoma, assessment of tumor location and size did not improve following contrast enhancement. Use of gadopentetate dimeglumine resulted in overestimation of stromal, parametrial, vaginal, and/or bladder wall invasion in eight patients. However, evaluation of intratumoral architecture and large lesions was easier with contrast-enhanced imaging. When only stage II and higher disease was analyzed, use of contrast material improved the evaluation of disease extent. The authors conclude that gadolinium enhancement adds to the accuracy of evaluation of endometrial carcinoma but is useful in only advanced cases of cervical carcinoma.

Adenocarcinoma↗
PubMed1991

Focal nodular hyperplasia of the liver: MR findings in 35 proved cases.

MR images of 28 patients with 35 lesions of hepatic focal nodular hyperplasia were reviewed to determine the frequency of findings considered typical of this condition (isointensity on T1- and T2-weighted pulse sequences, a central hyperintense scar on T2-weighted images, and homogeneous signal intensity). Fifteen lesions were imaged at 0.6 T with T1- and T2-weighted spin-echo (SE) pulse sequences; 20 lesions were imaged at 1.5 T with T1-weighted SE and gradient-echo pulse sequences and T2-weighted SE pulse sequences. Diagnosis of focal nodular hyperplasia was made pathologically in 25 patients, with nuclear scintigraphy in four, and with follow-up imaging in six. Only seven lesions (20%) were isointense relative to normal liver on both T1- and T2-weighted images. On T1-weighted SE images, 21 lesions (60%) were isointense relative to normal liver, 12 (34%) were hypointense, and two (6%) were hyperintense. On T2-weighted SE images, 12 lesions (34%) were isointense and 23 (66%) were hyperintense relative to normal liver. A central scar was present in 17 lesions (49%) and was hypointense relative to the lesion on T1-weighted images and hyperintense on T2-weighted images. Twenty lesions (57%) were of homogeneous signal intensity throughout the lesion, except for the presence of a central scar. All three MR imaging characteristics were present in three cases (9%). We conclude that hepatic focal nodular hyperplasia has a wide range of signal intensity on MR imaging.

Adult↗